Even for Beryl Bainbridge, the plain-speaking author of An Awfully Big Adventure who has an unerring nose for literary bull, this was deliciously wicked. A Booker prize bridesmaid for a record five times, Bainbridge, 64, has been scathing about book prizes and the ability of academics to judge them. Now she has turned her acerbic wit on literary pretension and its most common vice - bluffing about books you have not yet read.

When she was asked what her favourite book of the year was at the King's Lynn literary festival last week she picked an overlooked masterpiece called As Flies To Wanton Boys, by Rhoda F Cornstock.

According to several people attending the event, there was an immediate murmur of approval from the 100-strong audience.

Ms Cornstock, however, and her "intriguing depiction of incest in rural circles" was just a figment of Ms Bainbridge's imagination.

An actress in her youth, Ms Bainbridge kept a straight face throughout. Michael Holroyd, the biographer, and the novelist Paul Bailey, also on the panel, played along with the ruse, but finally Mr Bailey revealed the joke to the audience. Then, last night, it emerged that it was Mr Bailey who actually cooked up the prank.

Andrew Hewson, agent for Ms Bainbridge, said it was he who "found Ms Cornstock" and her neglected oeuvre. "The literary legend started with Paul. He and Beryl have corresponded about Ms Cornstock's work for some time." Norfolk was the obvious place to launch her ground-breaking novel on rural incest to an unsuspecting world.

Although there were whispers that some in the audience were angry that the joke was on them, Mr Hewson laughed off the episode. "Beryl was not insulting anyone. It was just a jolly old joke."

Her co-conspirator had gone to ground last night.

Ms Bainbridge knows all about the neglect that her imaginary protégé suffers. "Sometimes I wonder whether I'm being given prizes at my age out of sympathy or pity," she said after winning the WH Smith prize for Master Georgie, which missed out on the bigger prizes despite being described as the "best book ever not to have won the Booker".